ABSTRACT Air conditioning systems are the most viable source to avoid heat waves. Unfortunately, this puts a massive burden on the total electrical load. To deal with this critical issue, the Saudi Building Code National Committee has initiated the Saudi energy conservation code (SBC-602). This paper investigated the role of SBC-602 on the reduction of energy consumption in residential buildings. Furthermore, it also proposes the most effective building element to be insulated. A case study of energy consumption was modelled using SketchUp and analysed using OpenStudio Software. Inconsequence, three scenarios of U-values as an input in this work were suggested which are; building without thermal insulation, building with thermal insulation using Saudi electricity company (SEC) requirement, and using SBC-602 requirement. The study was conducted in three different cities Riyadh, Hail, and Abha, representing three climate zones in Saudi Arabia. Design of experiment (DOE) method was utilised to analyse the significant effects of the input factors. The result indicates that the decrease of the walls U-value is the most effective way to reduce the total electrical energy consumption. Moreover, decreasing roof U-value and increasing setpoint temperature were the following effective factor.